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Next, I received an emergency call today. When I got there and turned the power back on the furnace, Lennox - MD#G23Q2\3-75-2, the ID motor kicks on. Does the usual venting, then sends 24V to the pilot and ignitor, now here is where we get tricky... ignitor is sparking like a champ but the pilot won't lite. My first thought was no gas, not the case, I lite it with a Bic Stick. Furnace burners kick on and away she goes. So I go upstairs and turn the Stat down. Walk back down the stairs and of course the furnace is going through the normal shut down procedure. Instead of going upstairs again I jumper R + W, again the pilot won't light so I use the Bic. This time I pulled the flame sensor as I have narrowed the problem to the pilot igniting. The pilot lights up with the Bic and now I have an approx. 8" bright orange flame going to the middle HX opening... Now I'm lost... I was thinking maybe a crack in the HX because my thoughts were back to the basics of:

Then I had someone tell me that I have Orange and White mixed up! Can someone verify that and maybe shed some light on this damn pilot?? Oh, I replaced the gas valve just to be safe with one I had on the van and pilot does the same thing... Thanks for any input!

Is the pilot orfice and line cleen, I have seen on the g23 that the blue ignition control get week and did not put out enough spark to light the pilot. Replaced the ignition control and took care of problem. Also is the sensor ok.

Pilot and orifice line is clean, I pulled and cleaned as I checked the spark. I am getting 30v on the ignition and the sensor works great. I'm just mind boggled on that darn 8" flame from the pilot.... It is being sucked into the HX by the Inducer motor... checked the amp draw and I get 1.0 on both lines motor reads 1.5 on the label...

I thought those above are the right combo, am I wrong? If I am then why the heck does a camp fire burn yellow/orange? Should burn white according to him.. lol. Regardless I say crack. Anyone else? Gonna open the plenum tomorrow morning...

It sounds like there is more problems than a cracked heat exchanger. One way you could check to see if you have a crack on that furnace is pull the blower. That furnace has had problems with heat exchanger, it drops little rings in blower about the size of dime that is were they hold heat exchaner together and pops apart. also is the pilot 8 inches without indoor motor running.

Originally posted by hot wired sounds like pilot valve on gas valve is having problems.cracked hx usually burner flame turns yellow or rollout occurs with cracked hx.

New valve was installed, I checked the gas pressure = 3.5" W.C., and the flame is yellow/orange - 8" long - and it does roll. I just got thrown when another Tech reversed the colors on me... he is older and has, well thought had, more years in the field for exp. So he kinda made me second guess myself. Judging from the replies, I am right about the colors. And if I don't find a crack in that middle HX tomorrow I will definately be bamboozled! Never seen one like this before.

Originally posted by pipefitter2005 It sounds like there is more problems than a cracked heat exchanger. One way you could check to see if you have a crack on that furnace is pull the blower. That furnace has had problems with heat exchanger, it drops little rings in blower about the size of dime that is were they hold heat exchaner together and pops apart. also is the pilot 8 inches without indoor motor running.

Yes, I know this. Just never seen it before and wondered if anyone else had. Also wondered about the color thing... kinda threw me for a loop when he said it was opposite. Thanks for the quick replies all! I think I will stick around and learn from some of the vet's.. and who know's might even pick something up from someone new to the job...